Power supply
In a personal computer (PC), the power supply is the metal box usually found in a corner of he case. The power supply is visible from the back of many systems because it contains the power-cord receptacle and the cooling fan.
Power supplies, often referred to as "switching power supplies", use switcher technology toconvert the AC input to lower DC voltages.
The typical voltages supplied are:
3.3 volts
5 volts
12 volts
Power Supply Problems
The PC power supply is probably the most failure-prone item in a personal computer. It heats ad cools each time it is used and receives the first in-rush of AC current when the PC is switched on. Typically, a stalled cooling fan is a predictor of a power supply failure due to subsequent overheated components. All devices in a PC receive their DC power via the power supply.
A typical failure of a PC power supply is often noticed as a burning smell just before the computer shuts down. Another problem could be the failure of the vital cooling fan, which allows components in the power supply to overheat. Failure symptoms include random rebooting or failure in Windows for no apparent reason.